Regulation of superheat and feed water temperatures



Jan. 6, 1942. P. F. PoURcHoT l 2,268,776

REGULATION OF SUPERHEAT AND FEED WATER TEMPERATURES Filed March 6, 1941 l EUR E n 1. nw'IsNTOR. BYE m Patented Jan. 6, 1942 UNITED' STATE s PATENT OFFICE REGULATION OF SUPERHEAT AND FEED WATER TEMPERATURES Pierre Frederic Pourchot, Belfort, France, assignor to The La Mont Corporation, New York, N. Y.

Application March 6, 1941, Serial No.` 381,992 In Germany November 24, 1939 1 Claim.

this arrangement operation of the dampers doesV not result in the simultaneous regulation of the temperature of both the feed water and superheated steam because depending upon the position of the dampers, there will be a reduced impingement of heat in one of the passes and a corresponding increase of impingement of heat of the by-pass or parallel pass. Superheated steam temperature may be regulated by this means, but the feed water temperature remains entirely unaffected. The feed water temperature varies in accordance with the changes in boiler rating resulting in material disadvantages in that 1t is not possible to completely utilize the best temperature drop in the economizer and, consequently, that temperature stresses may occur in the boiler drum.

The present invention avoids these dicultiesK4 in a simple way. The steam generator has an oiftake duct divided into two parallel gas passes by means of a solid tube wall. In one pass superheater surface and the economizer are placed, and the steaming surface is located in the other of said passes. With this arrangement of the heating surfaces the operation of dampers controlling the passes regulates the superheated steam temperature and the feed water temperature simultaneously. By placing the economizer immediately behind the supreheater in the direction of gas flow and parallel to steaming surface the economizer becomes subject to the control of the dampers for the superheater pass and its bfy-pass. As the temperature characteristics of the superheater and economizer are substantially alike, the feed water temperature rises and falls in accordance with the boiler rating like the superheat. By maintaining the superheat temperature as nearly constant as possible, the feed water temperature is simultaneously maintained constant.

Heretofore it was customary to heat feed water CFI to a temperature substantially below the boiling point so as to avoid the formation of steam at peak loads as a result of exceeding the boiling temperature, which was undesirable. Since, according to the invention, the feed water temperature may be maintained constant, it now becomes possible to approach the boiling temperature in heatingL the feed water without causing steam formation by load changes.

As a further advantage of the invention it will be noticed that the dampers are arranged in a low temperature zone so that damage from burning the dampers is unlikely. When the boiler is of the forced circulation type it is an easy matter to separate the two parallel gas passes by forming a solid wall built out of tubes of the heat absorbing surface.y

The invention is described more fully hereafter in conjunction with the single figure of the accompanying drawing -which diagrammatically -represents a forced circulation boiler. The downflow gas pass is divided into two parts by a solid tube wall I0 thus forming two parallel gas passes.

In one of these gas passes steaming surface II- is arranged. In the other pass superheater surface I2- and economizer surface I3 are located. Beyond these heating surfaces in the direction of gas flow are control dampers I4 for each gas pass. the gases there is an air preheater I5. The advance heating surface I6 may be made as large as desired. As shownin the illustration, the separating wall I0 and the steaming surfaces II and I6 may be made into a common tube coil which is supplied by the distributer header I1 and delivers directly into the steam and water drum I8. 'I he feed water temperature is simultaneously regulated by means of the setting of dampers I4 in dependence upon the steam temperature. v

What I claim is:

A steam generator having an offtake duct for flue gases; steam generating tubes arranged to form a' solid wall dividing said oiftake duct to form two parallel gas passes; a superheater and an eccnomizer located in one pass; `steam generating elements disposed in the other pass;

and damper means fory controlling gas flow in said passes. I

PIERRE FREDERIC POURCHOT.

For further extraction of heat from 

